The last decade has seen the discovery of miRNAs in body fluids including plasma and serum. This lead to the hypothesis that RNAs play roles as extracellular signaling molecules . It is now clear that these RNAs exist not only in exosomes or other vesicles, but also outside vesicles bound to carrier proteins, such as Argonaute (Ago) proteins In vesicle-mediated RNA signaling, the vesicles are secreted by a large variety of cells, and contain RNAs (e.g. mRNA, miRNA and other ncRNA) that can be taken up by other cells. Strong evidence shows that they can be functional in other cells . In vesicle-free RNA signaling, exRNAs (e.g. siRNA and miRNA) could also be transported across cell membranes by specific receptors or channels, but evidence is much weaker for this mode . . Signaling via RNAs has the potential to play roles as autocrine, paracrine or endocrine signaling , and is therefore of great potential significance in many biological processes. It is now clear that most body fluids contain miRNA and other ncRNAs Moreover, these exRNAs are markers for various pathological states, including cancers and toxicity. Although previous studies have observed widespread signaling exRNAs, it is still not fully understood how and why source cells emit RNA, how they are transported, and how the target cells uptake and interpret the RNAs. It is also not clear when and why exosomal inclusion is needed, and how the inclusion affects biological function. In order to develop a comprehensive understanding of the complex mechanisms of this intercellular communication, a set of reference maps, an exRNA Atlas, is needed including a map of proteins and other carrier molecules that bind exRNA, as well as profiles of RNA content of exosomes and body fluids. To enable ^ the construction of an exRNA Atlas we will construct an automated en-exRNA pipeline for creating an exRNA Atlas Database by adapting existing RNA-seq workflows for mRNAs and miRNAs and develop advanced enexRNA analysis methods and tools for the community and for creating and exRNA Atlas Knowledge Base.